Liquid soap composition



United States Patent LIQUID SOAP COMPOSITION Lillian Lena Golub, .iamaica, and Herbert Smith Sylvester,

Whitestone, N.Y., assignors to Colgate-Palmolive Company, Jersey City, N.J., a corporation of Delaware No Drawing. Application June 14, 1954 Serial N 0. 436,716

3 Claims. (Cl. 252-132) The present invention relates to potassium liquid soaps and more particularly to potassium liquid soaps rendered non-corrosive to copper and copper base alloys.

Concentrated potassium liquid soaps have been widely used for washing the hands for many years because of the economy and convenience with which individual portions of these concentrates may be dispensed under sanitary conditions. Ordinarily these concentrates are dispensed from a dispensing device which is constructed in part from a copper base alloy such as brass, which generally is covered by a chromium plating. The chromium plating adds improved appearance to the device, and protects the copper base alloy from corrosion. In time however, the protective plating wears away, or porosities or pits develop in the plating, and the capillary active potassium-soap then contacts and corrodes the copper base alloy. Such corrosion has been found to result in a loss in metal and production of an unsightly, green-colored corrosion product.

It has now been found that by the incorporation of minute proportions of a certain class of chemical com-. pounds in potassium liquid soap concentrates it is possible to substantially inhibit or eliminate entirely the corrosive action of such concentrates on copper and copper base alloys such as are used in liquid soap dispensers. In accordance with the present invention such an inhibited composition comprises a solution of a potassium soap of a higher fatty acid in water, said soap being normally corrosive to copper and copper base alloys, and a small but effective amount, sufiicient to inhibit the corrosive action of said soap solution on copper and copper base alloys, of a compound selected from the group consisting of Z-mercaptobenzothiazole and alkali metal salts thereof.

The potassium soap of the present invention contains from about 12 to about 18 carbon atoms, may be saturated or unsaturated, and may be derived from fatty acids such as lauric, myristic, palmitic, oleic, and linoleic acids and mixtures thereof, for example, the fatty acids derived from coconut oil, red oil, palm kernel oil, palm oil, cottonseed oil, olive oil and olive oil foots, soybean oil, peanut oil, corn oil and mixtures thereof. These soaps may be prepared by a variety of means such as direct neutralization of the appropriate fatty acids or saponification of suitable fats and oils by potassium hydroxide. The soap may be prepared as an aqueous soap base containing as much as 55-65% solids. However, in the final aqueous concentrate prepared for dispenser use the potassium soap solids will be present in such an amount as to be completely soluble at ordinary room temperatures in the water employed as a solvent. This upper limit of solids content will vary somewhat depending upon the particular soaps employed and the composition of the concentrate, but normally will be about 40% by weight of the composition. The minimum amount of potassium soap solids will be about by weight of the final concentrate. The pH of the concentrate is adjusted by appropriate means, such as the addition of fatty acids or potassium hydroxide, to be within the range of about 8.5 to about 11.0, and preferably about 9.5 to 10.0, the upper limit of pH being established so as to insure mildness toward the skin of the user and the lower limit serving to eliminate the presence of free fatty acid and the likelihood of rancidity engendered thereby.

The Z-mercaptobenzothiazole or alkali metal salt thereof is normally present in a small but efiective amount sufficient to inhibit the corrosive action of the potassium liquid soap on copper and copper base alloys such as are used in liquid soap dispensers. Such amounts vary, depending on the particular composition involved, but amounts as low as about 0.019% and lower of the weight of potassium soap present in the composition are effective in certain potassium liquid soap compositions. Commonly, the Z-mercaptobenzothiazole or alkali metal salt thereof will not be present in an amount much more than 0.1% of the weight of potassium soap in the composition because suflicient protective action is achieved with lesser amounts of these corrosion inhibitors.

The compositions of the present invention may be pre pared simply by dissolving 2-mercaptobenzothiazole in an appropriate potassium liquid soap concentrate. However, although Z-rnercaptobenzothiazole is readily dissolved by concentrated aqueous alkali metal hydroxides, it is very slowly dissolved in alkaline liquid soap concentrates, and therefore it is preferred as a matter of convenience to employ an aqueous solution of an alkali metal salt of Z-mercaptobenzothiazole. Such solutions are conveniently prepared by dissolving 2-mercaptobenzothiazole in a concentrated aqueous solution of an alkali metal hydroxide, for example sodium, potassium or lithium hydroxide, and then mixing the resulting solution of the alkali metal salt of Z-mercaptobenzothiazole with a potassium liquid soap concentrate. By this procedure the inhibitor is rapidly and completely distributed throughout the body of potassium liquid soap to which it is added.

The following examples, in which all percentages are by weight, illustrate the effectiveness of Z-mercaptobenzothiazole and its alkali metal salts as inhibitors of corrosion by potassium liquid soap, but it is to be understood that the examples are illustrative only and that the invention is not limited thereby but only by the terms of the appended claims.

EXAMPLE I A potassium liquid soap concentrate is prepared in accordance with the following formula:

The concentrate may be perfumed, if desired. The potassium soap comprises a mixture of the potassium soaps of fatty acids derived from coconut oil and commercial oleic acid, these soaps being in the proportion of 3:1 by weight, respectively. The pH of the concentrate is buffered at about 10.0 by the borax.

A suitable test for evaluating the corrosive action of the compositions of the present invention consists of immersing a weighed square of copper foil, 5 cm. x 5 cm., in a solution of 70 ml. of the above potassium liquid soap concentrate in ml. of distilled water at room temperature for three weeks. The thickness of the copper foil is not critical, a typical value being 0.05 cm. An inhibitor is considered effective if the copper foil does not diminish: in weight by more than 5 mg, during the three weeks period.

Thus the above concentrate is divided into several 70 ml. portions and Z-mercaptobenzothiazole is dissolved with' stirring in'v'cert'ain' of these '70 ml. portionsfin accordance with the'data in Table I. To 'each 70 ml. portion there is'ad'cled 140 ml. of distilled water. Weighed pieces of copper foil, 5 cm. x 5 cm., are then immersed in each of the four preparations and maintained therein at' room temperature for three weeks, at the end of which time the pieces of foil are rinsed first in water and then in acetone, are dried, reweighed and the number of, milligrams net loss in Weight of the copper foil The surfaces of those pieces of copper which were not corroded remained bright and shiny, whereas the surfaces of, those pieces suffering a weight loss were darkenedrand discolored.

' The data of Table I illustrate that 0.019% of 2-mercaptobenzothiazole on a potassium soap basis adequately inhibits the corrosive action of the above soap composition. 7 EXAMPLE II A potassium liquid soap is prepared containing 65% water and 35% of a 3:1 mixture of the potassium soaps of coconut oil and red oil (commercial oleic acid). The pH of the composition is 9.5. To a portion of this mixture is added a 50% aqueous solution of inhibitor, the ,sodium salt of Z-mercaptobenzothiazole, in an amount :suchthat the composition contains 0.019% of the said sodium salt on a potassium soap basis. The inhibited ,and uninhibited compositions are tested according to the procedure set forth in Example I. The net losses in weight .after three weeks exposure are:

:Inhibited composition 1.1

,2,91a,sss r r t Similar results are obtained if the potassium or lithium salt of 2-mercaptobenzothiazole is employed in the place of the sodium salt thereof. n

It is obvious to one skilled in the art that various adjuvant materials may be used in conjunction with the potassium liquid soap compositions of the present invention. Thus, it is contemplated to prepare such compositions containing alcohols, glycerol, pine oil, perfumes, germicides, oxidizing agents, bleaches, coloring materials, fluorescent materials, emollients and cosmetic agent's...

Although the present invention has been described with reference to particular embodiments and examples, it will be apparent to those skilled in. the art that variations and modifications of this invention can be made and that equivalents can be substituted therefor without departing from the principles and true spirit of the invention.

Having thus described the invention, what is claimed is:

1. A concentrated potassium liquid soap comprising a solution of from about 5% to 40% by weight of a potassiumsoap'of a higher fatty acid in water and from about 0.019% to 0.1% by weight of said soap of a compound selected from the group consisting of Z-mercaptobenzothiazole and alkali metal salts thereof, said mercaptobenzothiazole compound being eifective to inhibit the corrosive action of said liquid soap concentrate on copper.

2. A liquid soap composition as set forth in claim 1 having a pH within the range of about 8.5 to 11.0.

3. A liquid soap composition as set forth in claim 1 wherein said higher fatty acids are derived from coconut oil fatty acids and oleic acid in the ratio of about 3:1 by weight.

References Cited in the file of this patent UNITED STATES PATENTS 1 1,970,564 Hoover Aug. 21, 1934 FOREIGN PATENTS 701,168 Great Britain Dec. 16, 1953 OTHER REFERENCES Chemical Formula, Bennett, Chem. Pub. Co., N.Y., vol. 4 1939 page 491.

, Sequestrene, AlroseChem. Co., Providence, R.I., 1952, pages 38-39. 

1. A CONCENTRATED POTASSIUM LIQUID SOAP COMPRISING A SOLUTION OF FROM ABOUT 5% TO 40% BY WEIGHT OF A POTASSIUM SOAP OF A HIGHER FATTY ACID IN WATER AND FROM ABOUT 0.019% TO 0.1% BY WEIGHT OF SAID SOAP OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2-MERCAPTOBENZOTHIAZOLE AND ALKALI METAL SALTS THEREOF, SAID MERCAPTOBENZOTHIAZOLE COMPOUND BEING EFFECTIVE TO INHIBIT THE CORROSIVE ACTION OF SAID LIQUID SOAP CONCENTRATE ON COPPER. 